<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>动态登录界面</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: '微软雅黑', sans-serif;
        }

        body {
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            background: linear-gradient(45deg, #ff6b6b, #4ecdc4);
            overflow: hidden;
        }

        .container {
            position: relative;
            width: 380px;
            padding: 40px;
            background: rgba(255, 255, 255, 0.95);
            border-radius: 20px;
            box-shadow: 0 15px 35px rgba(0, 0, 0, 0.2);
            transform: translateY(20px);
            opacity: 0;
            animation: slideUp 0.8s cubic-bezier(0.18, 0.89, 0.32, 1.28) forwards;
        }

        @keyframes slideUp {
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        .login-box {
            position: relative;
        }

        h2 {
            text-align: center;
            color: #2d3436;
            margin-bottom: 40px;
            font-size: 2em;
        }

        .input-group {
            position: relative;
            margin-bottom: 30px;
        }

        .input-group input {
            width: 100%;
            padding: 15px;
            border: none;
            border-bottom: 2px solid #ddd;
            outline: none;
            font-size: 16px;
            transition: 0.3s;
            background: transparent;
        }

        .input-group label {
            position: absolute;
            left: 15px;
            top: 50%;
            transform: translateY(-50%);
            color: #666;
            pointer-events: none;
            transition: 0.3s;
        }

        .input-group input:focus ~ label,
        .input-group input:valid ~ label {
            top: -5px;
            font-size: 12px;
            color: #4ecdc4;
        }

        .input-group input:focus,
        .input-group input:valid {
            border-color: #4ecdc4;
        }

        .button {
            width: 100%;
            padding: 15px;
            background: #4ecdc4;
            color: white;
            border: none;
            border-radius: 30px;
            cursor: pointer;
            font-size: 16px;
            transition: 0.3s;
            transform: scale(1);
        }

        .button:hover {
            background: #45b7b0;
            transform: scale(1.05);
        }

        .links {
            text-align: center;
            margin-top: 25px;
        }

        .links a {
            color: #666;
            text-decoration: none;
            font-size: 14px;
            transition: 0.3s;
        }

        .links a:hover {
            color: #4ecdc4;
        }

        /* 动态背景装饰 */
        .deco {
            position: absolute;
            background: rgba(255, 255, 255, 0.1);
            border-radius: 50%;
        }

        .deco:nth-child(1) {
            width: 150px;
            height: 150px;
            top: -70px;
            left: -70px;
            animation: float 6s infinite;
        }

        .deco:nth-child(2) {
            width: 100px;
            height: 100px;
            bottom: -50px;
            right: -50px;
            animation: float 5s infinite 0.5s;
        }

        @keyframes float {
            0%, 100% { transform: translateY(0); }
            50% { transform: translateY(-20px); }
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="deco"></div>
        <div class="deco"></div>
        <div class="login-box">
            <h2>用户登录</h2>
            <form action="/login" method="post">
                <div class="input-group">
                    <input type="text" name="username">
                    <label>用户名</label>
                </div>
                <div class="input-group">
                    <input type="password" name="password">
                    <label>密码</label>
                </div>
                <button type="submit" class="button" name="submit">立即登录</button>
                <div class="links">
                    <a href="#">忘记密码？</a>
                    <a href="#">注册账号</a>
                </div>
            </form>
        </div>
    </div>

    <script>
        // 添加简单的交互效果
        document.querySelectorAll('input').forEach(input => {
            input.addEventListener('focus', () => {
                input.parentNode.style.transform = 'scale(1.02)';
            });
            input.addEventListener('blur', () => {
                input.parentNode.style.transform = 'scale(1)';
            });
        });
    </script>
</body>
</html>